The standard car manual has 54/55 info in it.
My 59 to 64 "Shop Manual" has "D" body info in the back with the rest of the body info.
As far as the mechanical, the "D" body is pretty much the same for 53 thru 64, cars. Most all of the Stude lineup is pretty close. Even the Avanti suspension is the same as the rest of the cars. As with all of the body's, only the particular body differences would be noted in different manuals.
Much like the 53 to 55 sedan car. Very much the same as the 54-55 wagons, except for the tail gate info.
Though, I assume that there is actual 53 to 59 (?) manual.
Contact Studebaker International. See what they have. Or, look into these -
https://www.studebakervendors.com/literature.htmGood luck.
Mike